Molded articles and films

ABSTRACT

A method is disclosed for the preparation of a variety of molded articles and films prepared from gels of crosslinked starch xanthate. A nonexclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

aher Jan. 22, 1974 [54] MOLDED ARTICLES AND 3,233,193 3/1966 Tuschhofi 260/2335 I751 Inventor: George Meter, Dunlap, ifiiijii 3/1332 iisi ri fiiijjil... 1113 3652 18 [73] Assignee: The United State f America as 3,730,829 5/1973 Maher 260/2335 represented by the Secretary of Agriculture Washington Primary ExaminerTheodore Morris 22 Fi Jan, 24, 1973 Attorney, Agent, or Firm-Howard Silverstein: [21] AppL No 326,220 DEXlQaG-M QQHDQU .7

Related 1.1.8. Application Data 57 ABSTRACT 62] Division of Ser. No. 190,319, Oct. 18, 1971, Pat. No.

3,730,829. A method is disclosed for the preparation of a variety of molded articles and films prepared from gels of [52] US. Cl. 106/214, 162/175 crosslinked starch xanthate. [51] D211 3/28 C 25/02 Cosh 27/04 A- nonexclusive, irrevocable, royalty-free license in the i Cosh 27/14 invention herein described, throughout the world for [58] Flew of searchlow 214; 260/173 all purposes of the United States Government, with 260/2335- the power to grant sublicenses for such purposes, is hereb ranted to the Government of the United [56] Refmnces Cited States of America.

UNITED STATES PATENTS Lancaster 260/2335,

5 Claims, N0 Drawings Mower) ARTICLES AND FILMS This is a division of application Ser. No. 190,319 filed /18/71 now U.S. Pat. No. 3,730,829.

BACKGROUND OF THE INVENTION This invention relates to the preparation of molded articles and films having properties which vary from hard and brittle to soft and pliable. More specifically, the invention relates to products prepared from crosslinked starch xanthate. Reactions which crosslink carbohydrates, especially polysaccharides, through their hydroxyl groups are fairly well known. Crosslinked dextran, molecular sieves, and crease-resistant cotton cellulose fibers are among the more important products of this type. However, the amount of crosslinking or the degree of substitution (D.S.) attained in these products in quite low. Furthermore, to obtain the desired results in preparing the above-mentioned products, it is often necessary to use various combinations ever, these rigid gels were not firm enough to maintain the shape of a mold when removed therefrom and when dried, they resulted in gummy masses. Gels prepared from polyacrolein and sodium starch xanthate (D.S. 0.22-0.44) were exceptional in that they dried to hard, brittle, glasslike products. In the prior art teachings of the above reactions, it is indicated that the reactice moiety of the crosslinking agents react only with xanthate groups in sodium starch xanthate and that, while a long chain between crosslinking sites is not al ways necessary for gel formation, the molecular size of the connecting bridge should be considerable to impart insolubility to the product. I

I discovered that hard products, such as molded articles and films, which retain the shape of a mold were formed when sodium starch xanthate having a xanthate D.S. of from about 0.05 to about 0.60 was reacted with an excess of an alkyl diglycidyl ether such as 1,4-butanediol diglycidyl ether or an alkyl diepoxide such as butadiene diepoxide in an alakaline aqueous medium. The excess of the diepoxides was from about 2 to about 5 times the stoichiometric amount of one epoxide group per xanthate group in the sodium starch xanthate starting material. Placticizers were added in amounts of 0 to 200 percent of the dry weight of the sodium starch xanthate. The reaction was conducted in a mold for a time sufficient to allow formation ofa solid mass. This solid mass was removed from the mold and allowed to dry. In some instances dyes or fillers were added to the reaction mixture in sufficient quantity to impart color to the molded articles. Materials such as brom cresol purple, carbon black, potassium permanganate, sudan black, congo red, halopont blue, methylene blue, brom thymol blue, cresol red, or'any other compatible compound which can impart color can be used in this manner.

The reaction of sodium starch xanthate with diepoxides is homogenous, very rapid (at least at the start),

requires no heating or catalyst, and takes place in a simple, alkaline water medium. The crosslinked products first form opaque, gel-like masses that coalesce to solids which, as they form, come out of solution in one piece or mass, and the residual liquid medium quickly exudes or weeps from the solids. The solid masses dry to form materials which have properties that vary from soft and flexible to tough and nonflexible to brittle depending on the ratio of xanthate to diepoxide. Molded products retain sharp clear letters when the reaction takes place in a mold having embossed lettering. At early stages of formation, the instant products could lend themselves to compression molding. Colors of nondyed products range from white to yellow depending on the amount of diepoxide reacted. The products do not melt, but they do burn freely. They are essentially insoluble in such solvents as benzene, toluene, hexane, dioxane, methyl cellosolve, ethyl ether, ethanol, butanediol, acetone, glacial acetic acid, pyridine, chloroform, carbon tetrachloride, and dimethyl sulfoxide.

The simple molding characteristics of the instant products make them especially useful for casting and molding small pieces, sealants, films, adhering films, reinforced fiber cloths and mats, protective coverings of films as reinforced film fiber, plain or reinforced gaskets, stretchable gaskets, and pliable fillers.

l have further discovered that paper having increased I burst, wet and dry strength, and fold endurance, results from first reacting sodium starch xanthate having a xanthate D.S. of from about 0.1 to about 0.6 with an excess of an alkyl diglycidyl ether or an alkyl diepoxide, the excess being from 2 to 5 times the stoichiometric amount of one epoxide group per xanthate group in the sodium starch xanthate; then adding the resulting reaction mixture to a papermakers pulp suspension in amounts that result in levels of addition of from about 2.5 to 10 percent based on total weights of reactants and dry pulp; then allowing the resulting pulp mixture to stand from about 0.5 to about 18 hours; forming water-laid paper from the pulp mixture; and finally drying the paper.

Paper having essentially the same properties as above can be prepared by separately adding the same quantities of reactants to the papermakers pulp, allowing the mixture to stand from 0.5 to 18 hours, and finishing the process in the same manner.

DETAILED DESCRIPTION OF THE INVENTION The crosslinking reaction of sodium starch xanthate with an alkyl diepoxide is the basic element in this invention. Therefore, for the purpose of the invention, conducting the reaction in a mold to form a molded article is considered to be equivalent to conducting the reaction on a flat surface to form a film.

Sodium starch xanthate solutions (pH 1 1) having a 10-13 percent dry substance content were prepared as described by Swanson et al., Ind. Eng. Chem., Prod. Res. Develop. 3: 22 (1964) and Doane et 211., Die Staerke 17: 77 (1965). Each solution was used within 12 weeks after preparation (see Example 8, infra) since there is some decomposition and loss of D.S. after that time. The xanthate solutions were analyzed for dry substance starch and for xanthate groups from which D.S. and dry substance starch xanthate content based on the anhydroglucose unit (ACU) were calculated as described by Doane et al., supra.

Commercially obtained diepoxide crosslinking agents without further purification or modification were reacted with sodium starch xanthate. The following types of diepoxide compounds are considered suitreacts with one epoxide group. The ratio of epoxide groups to xanthate groups will be known herein as the S-ratio.

Attempts were made to follow the reactions by meaable for use in the instant invention; W HM 5 suring viscosity development with a Brookfield viscometer, but this proved to be difficult since in most cases k n nd i CHPCH CHI CHZCH,CH2CHI O CHQ 6H CHZ the reactlon quic 1y produced too stro g gels a sol d M precipitates. However, a few viscoslty measurements l4-butanediol diglycidyl hexane--. a a--- W W Table 1 Reactants Viscosity, cp

Sodium starch hours of reaction xanthate, D.S. S'ratio" 4 28 52 76 1 Ratio ol epoxide groups to sodium xanthatc group. 2 Dicpoxidc, l,4-butane1.liol diglycidyl ether.

where R starch, R CH -O-CH -CH:;-, or +CH where .r 0-4, and D.S. degree of substitution of sodium xanthate on the starch. According to Usually, when the gels attain viscosities over 10,000 cp, the spindle of the viscometer creates a hole or crack in the gel that does not close after the spindle is removed making further viscosity measurements useless.

Gel formation is a good indicator of crosslinking and reaction progress. Another such indicator is the disappearance of the yellow color, typical of the sodium starch xanthate solution after the alkyl diepoxides are added. The reactions were terminated at various times by pouring the reaction mixture into 95 percent ethanol to form a solid precipitate which was then analyzed for sulfur content by the method of White, Microchim. Acta, 807 (1962). Infrared (IR) absorption spectra were obtained on Nujol mulls between NaCl discs. The reactions shown in Table 2 were conducted in closed vials in order to more easily measure viscosity and to form products which could be manipulated for analysis. Reaction times were determined by sulfur analysis and ultraviolet absorption analysis of the supernatant reaction solution. Reactions were considered to be ended when all of the xanthate moieties in the starting material were reacted. No free sulfur was found in the reacthe above stoichiometry, one sodium xanthate group tion medi n.

Table 2 Product analysis Xanthate Reaction Cale. epoxide D.S. S-ratio time Appearance C=O 7cS D.S. ratio 7 0 .13 [-1.5 0.5-8 Fluid 0.13 2 0.5-4 Soft gel 0.13 3 8 Firm gel 0.13 5 0.5-8 Firm gel No 0.13 12 0.5 Firm gel No 0.38 1l.5 0.5-4 Fluid No 0.38 2 0.5 Soft gel No 8.84 2.0 0.38 2 0.5 Soft gel No 9.19 1.7 0.38 3 0.5 Firm gel Yes 0.38 5 0.5 Firm gel Yes 7.65 3.1 0.38 5 0.5 Firm gel Ycs 7.77 30 0.48 ll.5 0.5-4 Fluid No 0.48 2* 0.5 Soft gel No 0.48 3 V 0.5 Firm gcl Ycs Table 2 Conth u ed Product analysis Xanthate Reaction Calc. epoxide D.S. S-ratio time .Appearance C=O 7:5 D.S. ratio 0.48 5 0.5 at; 51 Ye? 0.48 10 0.5 Firm gel Yes I Calculated from sulfur analysis.

2 Ratio of epoxide groups per xanthate group. 3 Diepoxidc. 1.4-butanediol diglycidyl ether. 4 Determined by IR at 5.75 t.

As indicated in the table, the gelling rate and extent are dependent on the D.S. of the starch xanthate, being the least withthe low D.S. and increasing as the D.S. increases. Gelling also depends upon the amount of epoxide used. Reactions with the starting materials having S-ratios of l1.5 did not result in appreciable gelling or viscosity increases at all D.S. levels and over reaction times extended to several days. Reaction products described in Table 2 as being firm gels when left overnight in their reaction vials, harden to form solid handleable masses. A handleable mass or product is defined herein as having the ability to be removed from its container without significant distortion. Those products described as being soft gels harden to form solid handleable films when their respective reactions are performed as described in the examples, infra. Times sufficient for handleable products to form depend on the D.S. level of the sodium starch xanthate and the amounts of alkyl diepoxide added. These times are usually from 8 to 72 hours. Prior art indicates the alkyl diepoxides will not react with starch except in the presence of catalyst or relatively high pHs, nor will they polymerize under the reaction conditions of the instant method. It was unexpected, therefore, when l discovered that alkyl diepoxides reacted with sodium starch xanthate in more than the supposed stoichiemetric quantities (i.e., S-ratios greater than l). The reactions were conducted at room temperature (about C.) in the light in an aqueous medium having a pH of about 1 1.

Sulfur analysis of products obtained from reaction mixtures containing a twofold excess of epoxide groups indicates that 2 moles of epoxide groups (or 1 mole of diepoxide) per xanthate group had reacted. Similar reaction media containing a fivefold excess of epoxide groups produced a crosslinked material that contained only 3 moles of epoxide groups per mole of xanthate group. This limitation of epoxide addition indicates that the diepoxides are not polymerizing. Perhaps the presence of the xanthate group on the starch somehow activates starch hydroxyls, and the excess epoxide groups are reacting with these activated functional groups.

The existence of a carbonyl band at 5.75 it in the IR spectra of the product obtained from the reaction of 1,4-butanediol diglycidyl ether with sodium starch xanthate is evidence that the epoxide has attached to a xanthate group which is on a secondary carbon adjacent to a carbon containing a hydroxyl group. Similar structures are known to spontaneously rearrange so that their lR spectra show a peak at 5.75 t.

Reactions of sodium starch xanthates having low D.S. levels with alkyl diepoxides cast on a glass surface result in products which are thin,smooth brittle and clear. As the xanthate D.S. is increased, the resulting films become thicker, rougher, more opaque, and tougher. The effect of adding plasticizers such as glyc- .erol, l,4-butanediol, dipropylene glycol, and ethylene glycol to reaction mixtures containing the prescribed -reactants in various combinations of xanthate D.S. levels and S rati0s is to increase the strength, flexibility, and elasticity of the products. Films were also cast which incorporated cotton cheesecloth, and randompiled and nonwoven fiber glass cloth, and woven fiber glass cloth. These showed a very significant synergistic 25 effect on the strength of the resulting products, which in some cases were 20 to 50 times stronger than either the film or the cloth alone.

There is no preferred xanthate D.S. level, S-ratio, or amount of plasticizer within the operable limits of the instant method. It is my belief that from the procedures and discussions herein disclosed those skilled in the art r can, without excessive amounts of experimentation, determine the reaction parameters and combination of reactants and additives which would result in products having the most useful physical properties for their purposes.

The reaction described above between sodium starch xanthate and alkyl diepoxides, when incorporated into the production of paper, results in products having increased wet and dry strength. However, in this application, the reaction is conducted under conditions that prevent formation of solid masses. This can be accomplished by using starch derivatives having low to medium xanthate D.S. levels (e.g., 0.1 to 0.2) and diepoxides in low S-ratios (e.g., about 2), by using short reaction times with materials having higher D.S. levels, by conducting the reaction in dilute solutions or by conducting the entire reaction in the papermaker's pulp suspension. For example, when a starch derivative having a xanthate D.S. of about 0.1 was reacted with 2 times the stoichiometric amount of 1,4-butanediol diglycidyl ether for up to 76 hours, the product remained a soft gel. A similar reaction conducted for 5 minutes ex situ (i.e., outside the paper-pulp slurry) and 2 hours in situ (i.e., in the paper pulp slurry) resulted in a product which had extraordinary resistance to the MIT fold test (see Example 24, infra). Reactions of sodium starch xanthates having D.S. levels of up to 0.6, with diepoxides in S-ratios of about 3, conducted in dilute solutions do not gel but form turbid suspensions. lf the reaction medium is sufficiently dilute (see Example 20, infra), solid masses do not form upon standing for as long as 55 hours.

In one of the two preferred papermaking procedures,

sodium starch xanthate and an alkyl diepoxide in pre ferred S-ratios of about 3 are reacted ex situ in an aqueous medium for about 5 minutes and reacted in situ for from 0.5 to 18 hours. In a reaction time of O.5 hour essentially all the xanthate moieties have reacted as is indicated in Table 2, supra. However, Example 24, series 2, indicates reaction times of up to 6 hours Fisher Scientific Company, Fair Lawn, New Jersey). After mixing, 45 g. of an 8.68 percent, 0.15 D.S. sodium starch xanthate solution of pH 11 to 12 (made from ordinary pearl corn starch, product of CPC International, lnc., Englewood Cliffs, New Jersey) was weighed in quickly, and rapid mixing was continued until the mixture began to thicken or develop turbidity (a matterofa few minutes). v

b. 45 ml. of water, 1.8 ml. (1.958 g.) of Araldite RD-2 6 ml. (7.56 g.) of glycerol, and 45 g. of a 10.10 percent 0.25 D.S. sodium starch xanthate solution.

c. 45 ml. of water, 4.0 ml. (4.351 g.) of Araldite RD-2 6 ml. (7.56 g.) of glycerol, and 45 g. ofa 13.74 percent 0.51 D.S. sodium starch xanthate solution.

After the thickening point was reached, the mixtures were poured into a 145 mm. (5.75 in.) diameter glass Petri dish which was covered and set at ambient room conditions (25 C.) for 24 or 72 hours. The liquid which exuded was measured. The separated, solid disk that had formed was rinsed with water and dried on a glass plate in the room air, turning occasionally on the plate which had been coated lightly with Dow Corning Fluid silicone, for several days. g

The entire foregoing experiment was repeated with the elimination of glycerol in the recipes.

The principal observations are tabulated below:

result in some increase in paper strength. Levels of addition for the reactants is from 2.5 to 25 percent based on the dry weight ofthe paper pulp which, in the examples (infra), is an unbleached, softwood, sulfate papermakers pulp containing 75 percent by weight moisture. The moisture was taken into account in calculating levels of addition. When the sodium starch xanthate D.S. level is high (about 0.6), a 2.5 percent level of addition in sufficient. At lower xanthate D.S. levels increasing the level of addition significantly increases the paper products wet strength and resistance to the 5 MIT fold test. The second preferred procedure for producing paper is one in which the entire reaction of sodium starch xanthate with alkyl diepoxides is conducted in situ. Reactants in the same amounts as described above added separately to a papermakers pulp suspension and allowed to react for the same lengths of time resulted in products of superior strength to those prepared by procedures described in the prior art, using commercial paper strength additives. Example Z B infra, i nd icates that, when the alkyl diepoxides are added first and so- Time D.S. (hr.) Glycerol 0.51 24 No 72 No 24 Yes 72 Yes 0.25 24 No 72 No 24 Yes 72 Yes 0.15 24 No 72 No 24 Yes 72 Yes Exuded liquid lml.) Comments on film 25 Thick, rough, firm, shriveled, opaque pad 45 Thick, rough, firm, shriveled, opaque pad Thick, fairly smooth, pliable, opaque pad Thick, fairly smooth, pliable, opaque pad 13 Thick, brittle, shriveled, opaque film 22 Thick, brittle, shriveled, opaque film 9 Thick, smooth, pliable, opaque film l8 Thick, smooth, pliable, opaque film 0 Thin, smooth, brittle. cracked, clear film 0 Thin, smooth, brittle, cracked, clear film 0 Thin, smooth. pliable, clear film 0 Thin, smooth. pliable, clear film These casts from 0.15 D.S. xanthates do not separate from the dish walls but can be cut away. The clear films are yellow but transparent.

Casting as Film: EXAMPLE 1 H V V Reaction mixtures of the following three compositions were made, the first part (a) detailing the procedure. a. To 45 ml. of water were added 0.9 m1. (0.979 g., 3 times stoichiometric amount) of 1,4-butanediol diglycidyl ether (Araldite RD-2, technical grade, product of Ciba Products Company, Fair Laws, New Jersey) and 6 ml. (7.56 g.) of glycerol (certified reagent EXAMPLE 2 To 45 ml. portions of water added 3, 4, or 5 ml. (3.78, 5.04, or 6.30 g.) ofglycerol and 0.34 to 1.70 ml. (0.369 to 1.845 g.) of 1,4-butanediol diglycidyl ether in multiples of 0.34 ml. Then weighed in and mixed rapidly 45 g. of a 10.93 percent 0.13 D.S. sodium starch xanthate solution, giving reaction mixtures with l to 5 times the stoichiometric amount of the ether. The mixtures were cast in the covered Petri dish for 3 days and then processed as in the preceding experiment.

The dried films were cut into strips lnstron tested for tensile properties according to ASTM Designation D 882-64 T for thin plastic sheeting after equilibrating for 48 hours or more according to ASTM Designation D 618. An lnstrong testing machine was used. The following table summarizes the results:

Tensile Elongation Breaking strength Elastic Glycerol at break factor at break modulus S-ratio' ('1') (7r) (ll'L/in.) (p.s.i.) (p.s.i.)

l 76 No strength in wet cast, not handleable 2 76 471 28,389 3 76 61) I0 449 22,728

Table Continued Tensile Elongation Breaking strength Elastic Glycerol at break factor at break modulus S-ratio' (7:1 (71) (lb./in.) (p.s.i.) (p.s.i.)

1 Ratio of epoxide groups per xanthate groups, or excess of epoxide groups based on stoichiometric reaction.

2 As percent of sodium starch xanthate dry weight.

Those films made with 100 percent or more of glyc- I u erol are tacky, the tack increasing with the amount of glycerol, and adhere to glass, metal, and wood or paper fairly well.

EXAMPLE 3 significant strength variations from the unribbed" 15 films.

Attempts to cure and dry casts from 0.50 D.S. xanthates on the screen were not as successful as the sheet was rather thick (over 1 mm.) and opaque and although pliable tended to disfigure some in the late EXAMPLE 5 Casting mixtures were made in accord with the practices of Examples 2 and 3 using varying amounts of glycerol and varying S-ratios of the epoxide, but using .0- 4an .QZZPQQQL t ,s lua t t mad f o Tensile Elongation Breaking strength Elastic Glycerol at break factor at break modulus S-ratio' (72) (1b./in.) (p.s.i.) (p.s.i.)

1 See table, Example 2. 2 As /1 of sodium starch xanthutc dry weight.

EXAMPLE 4 When casts, made in accord with recipes as in Exam-. ples 2 and 3 which contained 4 ml. of glycerol, were put on l/l6-inch mesh screens rather than glass to dry after being removed from the dish mold and washed, the resulting films were very pliable, tacky, clear, yellow, smooth on one side, and cleanly imprinted with the mesh of the screen on the other side, giving a nonslip surface. Shrinkage on drying was very slight because of the holding power of the coarse screen on the film, but the films were easily peeled from the screen. Tensile strength tests on the ribbed film revealed no a different corn starch than the oneused to make the 0.13 and 0.25 D.S. xanthates of Examples 2 and 3.

These mixtures were cast in the Petri dish molds in which a full circle of cheesecloth had been placed. Casts were also made without cheesecloth. After the clue processing, the films were rather clear and the cheesecloth was quite evenly impregnated in continu- 45 ous appearance with no voids or flaws. The composites Tensile Elongation Break strength Glycerol at break factor at break D.S. S-ratio (72) (lb./in.) (psi) Appearance 0.14 2 none 1.1 48

' 2 76 38 6.5 354 Flexible, no tack 3 76 30 13.6 670. Flexible. no tack 3 102 28 10.8 500 Very flexible, some tack 3 128 35 11.7 543 Very flexible, most tack 0.22 5 none 161 1.2 71

2 69 32 10.9 710 Opaque, flexible 5 69 20 14.3 845 Opaque. flexible 5 92 29 6.8 444 Opaque, flexible i l 15 24 7.3 474 Opaque, flexible 1 See table. Example 2.

2 As "/1 of the sodium starch xzmthnte dry weight.

3 No cheesecloth in these.

4 Only a half of the normal reaction mixture was cast at this D.S.

These data illustrate a synergistic effect of combination of cheesecloth and derivative as the cheesecloth alone has a break factor of 7 to 8 pounds per inch.

EXAMPLE 6 12 EXAMPLE 8 A study of the effect of the age of the sodium starch xanthate solution on film strength properties was made concurrent with Example 7, using the 0.05 D.S. starch d d l I 5 derivative in the same recipe mixture as in Example 7. To 45 of water were a l m of glyc' The strength test results on the films produced showed 1 1 2 or 3 the stolchlomemc amount f the no effects due to the aging of the xanthate solution thrdlepoxlde of Example Then 4 pomons of their ough the time steps 1, 7, and 12 weeks. The individual an 1 Percent sofjmm Starch xanthate or strength values were in very excellent agreement with a 10.94 percent 0.13 D.S. sodium starch xanthate, or 1() those in the table of Example 7 relating to the 005 an 1 1.24 percent 0.25 D.S. sodium starch xanthate, or us Xamhate a 13.21 percent 0.54 D.S. sodium starch xanthate solution made from the same starch as used in the xanthate A g 7 E M B 7 preparations of Example 5 were weighed in and mixing A. To 45 ml. of water was added a 3 times stoichioaccomplished. The mixtures were cast in the Petri metric amount of the diepoxide of Example 1.. Then dishes which contained a full-cut circle of a randomadded 3 ml. (3.78 g.) of glycerol, 3 ml. (2.88 g.) of piled, nonwoven fiber glass cloth or a flat cloth of mul- Epoxol 8-2B plastlCiZe (p of Swift an C0 1- tifilament, fiber glass strips, about one-sixteenth-inch P n) g 0r 3 m1. Of Flexol EPO p1ast1- wide, woven loosely together at nine strips per inch, Clzer (p of Unlon Carbide p0r 0n. New 7.5 ounces (Sears, Roebuck and Company, Chicago, York, New York). Epoxol and Flexol and epoxidized Illinois). Casts were also made without fiber glass inlinseed oil and soybean oil plasticizers. Next 45 g. of corporation. Glycerol was added to all reaction mix- 1 a 9.48 percent 0.12 D.S. sodium starch xanthate solutures at ca. 70 percent of the dry weight of sodium tion or an 11.03 percent 0.22 D.S. sodium starch xanstarch xanthate. thate solution was weighed in and mixed. The mixtures Tensile Elongation Break strength Elastic Fiber at break factor at break modulus glass D.S. S-ratio (72) (lb./in.) (p.s.i.) (p.s.i.)

None 0.05 3 251 1.4 67.8 306 None 0.13 3 168 1.8 51.9 283 None 0.25 5 103 0.6 41.3 102 None 0.54 5 4.1 79.7 48.1 Nonwoven cloth only 12 3.2 35.6 327 Nonwoven 0.05 3 36 61.6 2,005 9,117 Nonwoven 0.13 3 42 44.8 1,493 5,817 Nonwoven 0.25 3 33 56.0 1,835 7,951 Woven cloth only 49 78.4 10,454 31,490 Woven 0.05 3 57 157.0 20,055 47,874 Woven 0.13 2 45 146.0 19.200 44,802 Woven 0.54 2 140.0 15,318 69,978

1 Only a half recipe mixture was cast. 2 See table. Example 2.

After due processing the composite films were tested for strength properties. Again a synergistic effect in the reinforcement was noted.

EXAMPLE 7 were cast and processed. After drying, the only pliable films were those containing glycerol. All the others were brittle, cracked, and oily feeling.

It was noted that the Epoxol seemed to promote faster reaction and turbidity development during mixing, and Flexol seemed to diminish the amount of shrinkage during curing.

B. To 45 m1. of water added 1 ml. (1.09 g.) of the diepoxide of Example 1. The amount of diepoxide is 3 times the stoichiometric amount needed for the amount of xanthate to be used. Next 3 ml. of one of the following agents was added as plasticizer:

1. 1,4-butanedio1, P6526 practical, (2) dipropylene Tensile Storage Elongation Break strength Elastic time at break factor at break modulus D.S. (wks.) (71) (1b./in.) (p.s.i.) (p.s.i.)

Glycerol is present in all reaction mixtures at ca. percent of the dry weight of sodium starch xanthate.

' practical, (4) triethylene glycol, P2828 practical. and

(5) ethylene glycol, 133; all products of Eastman Orgarlic emissls. Distillation P u t .Jndusfis. Rochester, New York.

After mixing, 45 g. of a 10.12 percent 0.12 D.S. so-

dium starch xanthate solution was added. The mixture was rapidly and well stirred until signs of thickening appeared and then poured into the Petri dish to cast. After being in the cast for 18 hours the soft, solid sheets were floated out of the dishes in water, rinsed -599?! a emar sesssd thr ugh. sh a sa ari I ether, ml. (0.38 of diepoxide (product of Columbia Organic Chemicals, Columbia, South Carolina), or 0.81 ml. (0.90 g.) of glycerol diglycidyl ether, (Aerite 100, product of Shell Chemical Company, New York, New York). Forty-five g. of a 10.46 percent 0.1 1 D.S. sodium starch xanthate solution was weighed in and the mixtures were cast.

The mixture made with glycerol digylcidyl ether did not result in the formation ofa solid entity and evaporation of liquid left a gummy deposit. The solid casts were processed, dried, and tested.

fi riaaa sel i fij ii si isi h di m m m All cast sheets were easily removable and handleable.

After drying for about 4 days, the films with the butanediol or dipropylene glycol were somewhat intermediate in pliability and could be broken on sharp bending. Films with hexanetriol or triethylene glycol on the other hand were very brittle and cracked upon slight bending. They also had a white surface bloom. 3

None of the films had an oily feel or surface as did those of Example 9A which contained Epoxol of Flexol.

Only the film made with ethylene glycol had a pliability approaching that of film made with glycerol as plasticizer. After about 3 weeks of drying at room conditions even the film with ethylene glycol becomes rather brittle, although remaining without bloom, whereas films with glycerol seem to remain flexible indefinitely.

, -.....-.EXA .I1EJ

To ml. portions of water added 3 ml. (3.78 g.) of glycerol. Then added 1,4-butanediol diglycidyl ether in multiples of 0.25 ml. increments starting with 0.50 ml. to provide mixtures with 2, 3, 4, and 5 times the stoi chiometric amount of the ether. Next 45 g. of a 9.48 percent 0.1 1 D.S. sodium starch xanthate solution made from a high-amylose content corn starch (Amylon 7, National Starch and Chemical Corporation,.

New York, New York) was weighed in and the mix tures were cast in the Petri dishes. After the usual processing, the strength character of the films was determined. It was noted that the films from the high amylose starch were about twice as thick as those from ordinary corn starch.

Tensile Elongation Break strength Elastic Glycerol at break factor at break modulus S-ratio' (7c) (7() (lb./in.) (p.s.i.) (p.s.i.)

2 90 No strength in wet cast, not handleable 3 9O 6.8 123 901 4 1 13 5.5 97 l ,380 5 90 310 6.7 124 1,860

I See table. Example 2.

2 As /t of dry weight sodium high amylosc sturch xanthate.

EXAMPLE 10 To 45 ml. of water added 3 ml. (3.78 g.) of glycerol. 55

Then added one of the following quantities of diepoxide, each representing a 3 times stoichiometric amoun- To 45 ml. protions of water added 3 or 4 ml. of glycerol. Then added 1.06 ml. of the above epoxide to pron ile Elongation Break strength Elastic Ratio, Glycerol at break factor at break modulus epoxide/xunthate (71) (71) (lb./in.) (p.s.i.) (p.s.i.)

I See table. Example 2.

2 As "i of dry weight high-amylose-stureh xanthate.

' Casting in Molds:

EXAMPLE 12 To ml. of water was added 1.14 ml. (1.24 g., 3 times the stoichiometric amount) of l,4-butanediol diglycidyl ether (Araldite RD-2, technical grade, product of Ciba Products Company, Fair Lawn, New Jersey). Then quickly 15 g. of a 12.69 percent 0.44 D.S.

, letters, (2) a glass tube, or (3) a cup making mold. The

molds were allowed to set overnight at about C. or room temperature. Inspection of the molds showed a solid, yellowish mass in the shape of the mold, separated from surfaces of the mold, and surrounded by exuded liquid. The solid masses were easily removed from the molds, washed with water, and dried several hours.

When this procedure was repeated using a stoichiometric or twice stoichiometric amount of the epoxide, unhandleable casts were obtained, respectively being a mushy suspension and a soft gel.

When this procedure was repeated 'with a 3 times stoichiometric amount of the diepoxide in reaction with 0.12 D5. or 0.24 D.S. sodium starch xanthate in place of 0.44 D.S., the casts from the lowest D.S. xanthate could not be removed from the molds, having exuded essentially no liquid; and those from the intermediate D.S. xanthate could be removed only with diffi- 'culty, having exuded only a small amount of liquid.

When this procedure was repeated every 2 days with an 0.42 D.S. xanthate over a 2-week period, no detectable differences in the casting characteristics were noted, indicating no effect due to xanthate age within this time period.

EXAMPLE 13 To 15 ml. of water was added 1 ml. (1.26 g.) or 2ml. (2.52 g.) of glycerol (certified reagent, Fisher Scientific Company, Fair Lawn, New Jersey) or 1 ml. (0.96 g.) or 2 ml. (1.92 g.) of Epoxol 8-2B plasticizer (product of Swift and Company, Chicago, Illinois). Then added 1.31 ml. (1 43 g., 3 times the stoichiometric amount) of 1,4-butanediol diglycidyl ether. 1n the manner of Example 12, 15 g. ofa 13.49 percent sodium tions. Every 48 hours the casts were weighed until essentially constant weight was reached in 8 days. The

characteristics of the dried casts related to the plasticizer use as follows:

Plasticizer Trimness Plasticizer retention 1 ml. glycerol 2nd softest 72% 2 ml. glycerol softest 697r 1 ml. Epoxol hardest. oily surface 2 ml. Epoxol 3rd softest, 100% oily surface 1 By weight determination.

Attempts to simulate the preceding experiment with glycerol, but with l0-ml. and 5-m1. amounts of water in place of 15 ml. and casting in the lettered box mold,

resulted in an evenly dried, sharply detailed, pliable plate only when 10 ml. of water was used and drying was done in the desiccator. Because of the rapid reaction, mixing is difficult and lumps are hard to avoid before getting the mixtures into the molds even in the case of 10 ml. of water usage.

EXAMPLE 14 To 10 ml. of water added 1.28 ml. (1.395 g., 3 times stoichiometric amount) of 1,4-butanediol diglycidyl ether. Then added small portions of the dye materials listed below, all except the carbon black dissolving. Next, in the manner of Example 12, 15 g. of 12.57 percent sodium starch xanthate solution (0.52 D.S.) was added and the stirred mixtures were cast in a small funnel. The casts were removed, washed, and dried in the ambient room air. The high D8. of the xanthate here and the lesser amount of water used results in more shrinkage and distortion than occurs with a ca. 0.40 stel ea s e smableawdust w th the desired color.

6. None 7. Halopont blue 8. Methylene blue 9. Brom thymol blue 10. Cresol red 1. Brom cresol purple 2. Carbon black 3. Potassium permanganate 4. Sudan black B 5. Congo red EXAMPLE 15 To 15 m1. of water added 1.32 m]. (1.440 g., 3 times the stoichiometric amount) of 1,4-butanediol diglycidyl ether, and 1.61 g. of either calcium carbonate mesh) or Darco Grade 60 carbon black (product of Atlas Powder Company, Wilmington, Delaware). Mixed well and weighed in 15 g. of an 11.92 percent sodium starch xanthate solution (0.58 D.S.) quickly, mixed further until viscosity development became apparent and then cast in the cup mold or the lettered box mold. The casts were removed, washed, and dried. The cup casts were somewhat pliable, with little distortion and shrinkage. The lettered box cast with carbon had little shrinkage and the lettering was quite clear and sharp. However, the box cast with carbonate was not good, and a blooming tendency of the carbonate destroyed the lettering detail.

Attempts to simulate the above experiment with 0.24

\ D.S. xanthate resulted in mushy casts.

EXAMPLE 16 To 15 ml. of water added 0.439 g. (3 times stoichiometric amount) of butadiene diepoxide (product of 17 Columbia Organic Chemicals, Columbia, South Caro lina). Then weighed in 15 g. of an 11.10 percent sodium starch xanthate solution (0.44 D.S.), mixed well, and let set in a glass tube. Although the behavior of this reaction mixture and the casting was much the same as shriveled, brittle, and fragile than those of Example 12.

When this procedure was repeated with a 0.24 D.S. xanthate and 3 times the stoichiometric amount of the diepoxide, a very brittle cast was also obtained. Incorporation with Papermaking Pulp:

EXAMPLE 17 those of Example 12, the resulting dried cast was more ment was noticeable on the bottom.

A 600-m1. suspension of the paper pulp prepared as t in Example 17 was added. The mixture was set at room conditions for 3 hours and then a mat was formed. This mat was also much the same as the mat of Example 17. Analysis of a ground portion showed 0.23 percent sulfur, d.b., corresponding to ca. 13 percent retention of per mole of xanthate group to be used. Then 15 g. of

an 8.96 percent 0.24 D.S. sodium starch xanthate solution was weighed in and mixed rapidly until reaction was underway as evidenced by thickening and clouding. The mixture was set at room conditions for 1 hour, at which time it was a soft, yellow, opaque, slowrunning gel. The gel was stirred into about 400 ml. of water to disperse.

The dispersed gel was stirred into a 1,400 ml. suspensionof unbleached, softwood, sulfate, papermakers pulp g. of 75 percent moisture, 800 ml. SR freeness pulp, product of Bemis Company, lnc., Peoria, lllinois, that had been soaked in ca. 600 ml. water and gently"arsmtegratd'ifi a Waring Blendor prior to final dilution).

The treated pulp suspension was set at room conditions for 3 hours, at which time the pulp had settled about one-third through the volume in the 2-1. beaker.

Some clear water was decanted and then the beaker was inverted over a 1/l6-inch mesh wire screen to permit drainage and formation of a thin mat. The mat was dried in the room air for several days. During drying and after drying, it was noted that the mat of treated pulp had a lighter hue and the surface appeared to have a denser or lessloose packing array of fibers than did a control mat made of untreated pulp in the same screen-forming technique. Also when dry, the treated mat was somewhat stiffer to hand. A portion of the dried mat was ground in a Wiley mill to 60 mesh and analyzed for sulfur content; found-0.25 percent, d.b. This content represents ca. 13 percent retention of the added sulfurous derivative, after allowing for a blank sulfur content of ca. 0.10 percent in the pulp itself.

EXAMPLE 18 To 250 ml. of water added the same amounts of diepoxide and xanthate as in Example 17. Mixed well and set for 1 hour. A milky suspension developed. This was added to a suspension of paper pulp in the same manner as in Example 17 and another mat was formed.

The character of this mat was much the same as that formed in Example 17. The analysis of the ground mat showed 0.25 percent sulfur, d.b., corresponding to ca. 13 percent retention of additive.

EXAMPLE 19 To ca. 1.400 ml. of water added the same amounts of diepoxide and xanthate as in Example 17. Let set at room conditions for 3 hours. The mixture became faintly turbid and a very small amount of solid sediderivative.

additive.

EXAMPLE 20 To 1,600 ml. of water added 15 g. of an 11.22 percent 0.22 D.S. sodium starch xanthate solution and 0.56 ml. (0.61 g.) of the diepoxide of Example 17. The amount of diepoxide is 3 times the stoichiometric amount of 1 mole epoxide group per mole of xanthate group. Mixed well and let set. By 7 hours afaint turbidity had developed. After 48 hours the turbidity was much more prominent and a fine precipitate was appearing. A 30-g. portion of the paper pulp, dispersed in 450 ml. of water, was stirred in and the mixture was processed into a mat.

EXAMPLE 21 To 15 ml. of water added 0.22 ml. (0.24 g.) of butadiene diepoxide (product of Columbia Organic Chemicals, Columbia, South Carolina) and 15 g. of the same xanthate used in Example 17. The amount of epoxide is 3 times the stoichiometric amount of 1 mole of epoxide group per mole of xanthate group. The mixture was set at room conditions for 1 hour. The ensuing gel was much stiffer than that of Example 17 and would not flow. It was gently broken up in a Waring Blendor in ca. 400 ml. of water.

It was added to a pulp suspension as in Example 17. In the 3-hour standing period, the pulp settled about one-third in the beaker. The character of the mat was much the same as that of Example 17, but analysis of the ground, dry mat for sulfur content found 0.22 percent d.b., indicated only 10 percent retention of added In about 250 ml. of water 15 g. of the pulp described in Example 17 was soaked for an hour, broken up with a stirring rod, and gently beaten (to a small vortex appearance) in a blendor. Then 2.98 g. of a 10.91 percent 0.26 D.S. sodium starch xanthate solution was slowly added to the beating pulp and mixing carried on about 5 minutes more. Then 0.13 ml. 0.146 g.) of the diepoxide of Example 17 was added dropwise while beating and an additional 5 minutes of beating was accomplished. The suspension was transferred to a beaker to set overnight (16-18 hours). In a matter of about 15 minutes a light, cloudy appearance developed in the suspension, without settling. The suspension was diluted to 800 ml. in a 1-liter beaker and formed into a mat. The mat was of noticeably lighter hue than a :mat from an untreated pulpcontrol. However, the de' termined sulfur content of the dried, treated mat indicated only a 7 percent retention of the treating prod-- as Example 22 except that the diepoxide was added to the beating pulp first, then the xanthate next. It was noted that the whitening appearance took about 2 4 hours in the setting step. Sulfur analysis indicated about 21 percent retention.

19 EXAMPLE 24 Three series of trials embodying variations and combinations of the procedures of Example 17-23 were established. The starch xanthates used were: 0.10 D.S., l 1.41 percent sodium starch xanthate; 0.26 D.S., 10.91 percent sodium starch xanthate; and 0.57 D.S., 11.16 percent soidum starch xanthate. The diepoxide was that of Example 17. y

The variations in procedures were as follows: Series 1 utilized a 5-minute ex situ (away from pulp) reaction between a given weight of the sodium starch xanthate solution and a given weight (3 times the stoichiometric amount) of the diepoxide in a weight of water equal to the weight of xanthate solution, followed by a 2-hour, unstirred, in situ (in presence of pulp) reaction of the Series 2-5 minutes ex situ reaction, varied in situ reaction, 2.5 percent addition level, 0.26 D.S. so- Ji smste s at ex situ m ss modest a te a a n; it oflmersent,

' Xanthate Addition Burst MlT Breaking length, m. Additive D.S. level,72 factor fold Wet Dry Experimental 0.57 60.6 980 255 7,790 Experimental 0.26 10 66.3 880 245 7,980

Experimental 0.57 2.5 54.6 1,000 220 7,330 Experimental 0.26 2.5 56.6 590 225 7,390 Experimental 0.10 2.5 5 l .l 500 200 7,230 Control 40.l 260 155 6,350 Gel'd. starch 2.5 44.9 350 175 6,670 Na starch xanthate 0.10 2.5 42.4 345 180 6,480 Comm. cat. 2.5 64.2 715 180 8,490

Series 3-18 hours in situ reaction, varied addition level, varied D.S., other additives paper additive.

suspension g. dry pulp in 750 ml. water) of pulp in a blendor with stirring. Series 2 was the same as Series 1 except that the length of the in situ reaction was varied. Series 3 involved only a constant in situ reaction in which during the pulp agitation process in the blendor the xanthate was added to the pulp first and then the diepoxide.

ln each Series the treated 2-percent pulp suspensions were diluted to 6,250 g. with water (distilled used throughout), dropped to pH 7 with muriatic acid as needed, and processed into handsheets. The dried handsheets were tested for strength properties, according to TAEPl standard methods as follows:

Tcst TAPPI Method No.

Burst strength T 403 ts-63 Breaking length: wet T 456 05-68 dr T 494 05-70 MlT fold T 511 su69 The results are in the following tables.

Series 1-5 minutes ex situ reaction, 2 hours in situ reaction, 2.5 percent addition level Breaking length, m.

I claim: 1. A method of preparing molded articles and films which comprises reacting a sodium starch xanthate said sodium starch xanthate, ofa plasticizer, said excess being from about 2 to about 5 times the stoich iometric amount of one epoxide group per xanthte group in said sodium starch xanthate, the reaction being conducted in a mold for a time sufficient to allow formation of a solid mass that is then removed from said mold and allowed to dry.

2. Molded articles and films prepared by the method described in claim 1.

3. Molded articles and films prepared by the method described in claim 1 in which the alkyl diglycidyl ether is 1,4-butanediol diglycidyl ether and the alkyl diepoxide is butadiene diepoxide.

4. Molded articles and films as described in claim 2 I which contain a dye in sufficient quantity to impart color tJsZfdii'rYiEks and films, said dyes comprising brom cresol purple, carbon black, potassium permanganate, sudan black, congo red, halopont blue, methylene blue, brom thymol blue, or cresol red.

5. Molded articles and films as described in claim 2 wherein cheesecloth or fiber glass cloth is incorporated as a reinforcing agent. 

2. Molded articles and films prepared by the method described in claim
 1. 3. Molded articles and films prepared by the method described in claim 1 in which the alkyl diglycidyl ether is 1,4-butanediol diglycidyl ether and the alkyl diepoxide is butadiene diepoxide.
 4. Molded articles and films as described in claim 2 which contain a dye in sufficient quantity to impart color to said articles and films, said dyes comprising brom cresol purple, carbon black, potassium permanganate, sudan black, congo red, halopont blue, methylene blue, brom thymol blue, or cresol red.
 5. Molded articles and films as described in claim 2 wherein cheesecloth or fiber glass cloth is incorporated as a reinforcing agent. 